Charger, Charging Method, and Program

The present disclosure generally relates to a charger, a charging method, and a program, and more particularly relates to a charger, a charging method, and a program, all of which are applied to an assembled battery for use in an electric tool.

Patent Literature 1 discloses a charging circuit for charging a battery pack for use in an electric tool.

Patent Literature 1: JP 2011-45224 A

A charging circuit (charger) as disclosed in Patent Literature 1 is required to shorten the charging time of the battery pack (assembled battery).

In view of the foregoing background, it is therefore an object of the present disclosure to provide a charger, a charging method, and a program, all of which contribute to shortening the charging time of an assembled battery.

A charger according to an aspect of the present disclosure is used in an electric tool. The charger charges an assembled battery, including an all-solid-state battery, with electricity. The charger includes a charging unit. The charging unit charges the assembled battery by constant current charging until a voltage value of the assembled battery during charging reaches a predetermined voltage value which is larger than a voltage value of the assembled battery in a fully charged state.

A charging method according to another aspect of the present disclosure is performed by one or more processors. The charging method is a method for charging an assembled battery used in an electric tool which includes an all-solid-state battery. The charging method includes charging the assembled battery by constant current charging until a voltage value of the assembled battery during charging reaches a predetermined voltage value which is larger than a voltage value of the assembled battery in a fully charged state.

A program according to still another aspect of the present disclosure is a program designed to cause one or more processors to perform the charging method described above.

A preferred embodiment of the present disclosure will now be described in detail with reference to the accompanying drawings. In the following description of embodiments, constituent elements illustrated on multiple drawings and having the same function will be designated by the same reference sign and description thereof will be omitted herein to avoid redundancy. Note that the embodiment to be described below is only an exemplary one of various embodiments of the present disclosure and should not be construed as limiting. Rather, the exemplary embodiment may be readily modified in various manners depending on a design choice or any other factor without departing from the scope of the present disclosure. It should also be noted that the embodiments (including their variations) to be described below may be adopted in combination as appropriate.

Note that the drawings to be referred to in the following description of embodiments are all schematic representations. Thus, the ratio of the dimensions (including thicknesses) of respective constituent elements illustrated on the drawings does not always reflect their actual dimensional ratio.

1 1 FIG. An overview of a charging systemaccording to an embodiment will be described with reference to.

2 5 5 3 5 5 A chargeraccording to this embodiment charges an assembled batterywith electricity. The assembled batteryis used in an electric tooland includes an all-solid-state battery. More specifically, the assembled batteryaccording to this embodiment includes a plurality of battery cells. All of the plurality of battery cells included in the assembled batteryaccording to this embodiment are all-solid-state battery cells.

2 21 21 5 5 5 The chargerincludes a charging unit. The charging unitcharges the assembled batteryby constant current charging until a voltage value of the assembled batteryduring charging reaches a predetermined voltage value which is larger than a voltage value of the assembled batteryin a fully charged state.

5 5 4 5 5 4 5 5 21 5 As used herein, the “voltage value of the assembled battery” refers to a voltage value between terminals of the assembled battery(or a battery pack), a voltage value between single battery cells, or a voltage value between a plurality of battery cells. In this embodiment, the voltage value of the assembled batteryis supposed to be, for example, a voltage value between terminals of the assembled battery(or the battery pack). Also, the “voltage value of the assembled batteryduring charging” herein refers to a voltage value of the assembled batterywhile the charging unitis charging the assembled batteryby constant current charging. Furthermore, the “fully charged state” herein refers to a state in which the state of charge (SOC) is, for example, 100%. Note that the “fully charged state” may also refer to a state in which the SOC is, for example, equal to or higher than 90%.

5 2 5 5 5 5 The assembled batteryusing the all-solid-state battery cells may be charged with a larger current than an assembled battery using, for example, lithium-ion battery cells. Furthermore, the chargeraccording to this embodiment charges the assembled batteryby constant current charging until a voltage value of the assembled batteryduring charging reaches a predetermined voltage value which is larger than a voltage value of the assembled batteryin a fully charged state, thus contributing to shortening the charging time of the assembled battery.

1 1 3 FIGS.- Next, a detailed configuration for the charging systemaccording to this embodiment will be described with reference to.

1 1 2 3 4 1 2 4 3 1 4 1 2 3 5 1 2 3 4 1 FIG. The charging systemaccording to this embodiment is used, for example, on an assembly line in which a workpiece is assembled at a factory. As shown in, the charging systemincludes a charger, an electric tool, and a battery pack. In the charging systemaccording to this embodiment, the chargercharges the battery packwhich may be removably attached to the electric tool. Note that the charging systemdoes not have to include the battery pack. Alternatively, the charging systemmay also include the chargerand an electric toolin which the assembled batteryis built. Still alternatively, the charging systemmay also include the single charger, a plurality of electric tools, and a plurality of battery packs.

2 FIG. 3 3 3 As shown in, the electric toolaccording to this embodiment is an impact rotary tool such as an impact screwdriver. The electric toolaccording to this embodiment is an electric tool that a user may grip with a single hand. Note that the electric toolis not limited to the impact rotary tool but may also be any other type of electric tool such as a drill screwdriver or a hammer drill.

3 4 3 4 3 4 5 The electric toolaccording to this embodiment is configured to be loaded with the removable battery pack. Note that the electric tooldoes not have to be configured to be loaded with the removable battery pack. Alternatively, the electric toolmay also be configured to have a built-in battery pack(or assembled battery).

1 FIG. 3 31 3 5 4 31 5 As shown in, the electric toolincludes a driving unit. The electric tooluses, as a power source, the assembled batteryof the battery packto activate the driving unitwith the electric power (i.e., electrical energy) supplied from the assembled battery.

31 31 5 31 3 The driving unitincludes a motor. The driving unitis configured to operate using the electric power supplied to the motor from the assembled batteryserving as a power source. Also, the driving unitincludes an output shaft that rotates when the motor is energized. A screwdriver bit for use to turn a fastening member such as a screw is removably attached to the output shaft. When the user pulls the trigger of the electric toolwith the screwdriver bit fitted into a tool hole of a fastening member, the screwdriver bit starts rotating, thus allowing for either tightening or loosening the fastening member.

3 2 5 4 3 2 5 3 5 3 2 3 2 2 FIG. When the user finishes or suspends his or her operations, he or she may load the electric toolinto the chargeras shown in. Then, the assembled batteryof the battery packattached to the electric toolmay be charged with electricity by the charger. In the same way, even in a situation where the assembled batteryis built in the electric tool, the assembled batterybuilt in the electric toolmay also be charged with electricity by the chargerby making the user load the electric toolinto the chargerwhen he or she finishes or suspends his or her operations.

4 3 4 3 4 5 1 FIG. As described above, the battery packaccording to this embodiment is configured to be removably attached to the electric tool. Alternatively, the battery packmay also be configured to be irremovably attached (i.e., fixed) to the electric tool. As shown in, the battery packincludes the assembled battery.

5 4 5 The assembled batteryaccording to this embodiment is housed, for example, in a housing of the battery pack. As described above, the assembled batteryaccording to this embodiment includes a plurality of all-solid-state battery cells. The plurality of all-solid-state battery cells according to this embodiment is implemented as a plurality of laminated battery cells (i.e., pouch cells) stacked in a predetermined direction.

5 The assembled batteryusing the all-solid-state battery cells may be charged with a larger current than an assembled battery using, for example, lithium-ion battery cells. That is to say, if the all-solid-state battery and the lithium-ion battery have the same electric capacitance, the all-solid-state battery may be charged more quickly than the lithium-ion battery.

4 2 5 3 2 4 2 Also, the battery packincludes power-receiving terminals to receive electric power supplied from the charger. The power-receiving terminals include at least one pair of terminals, namely, a high-potential terminal and a low-potential terminal. While the assembled batteryis being charged, a potential at the high-potential terminal is higher than a potential at the low-potential terminal. With the electric toolloaded into the charger, the power-receiving terminals of the battery packand the power feeding terminals of the chargerare mechanically and electrically connected to each other. As used herein, the phrase “electrically connected to” refers to connection in an electrically conductive state, which includes not only direct connection but also indirect connection via a conductor such as an electric wire, a circuit breaker, or relay (i.e., a connecting device).

2 5 2 3 3 2 3 2 2 3 2 4 2 3 4 2 FIG. The chargeris a device that may charge the assembled batterywith electricity. As shown in, the chargeraccording to this embodiment is configured to be loaded with the electric toolin a fixed position. That is to say, when the user finishes or suspends his or her operations, he or she may load the electric toolinto the charger, thus having the electric toolfixed to the charger. Note that the chargerdoes not have to be configured to be ready to fix the electric toolthereon. Rather, the chargeronly needs to be configured to be ready to fix the battery packthereon. Alternatively, the chargermay also be configured to be loaded with either a plurality of electric toolsor a plurality of battery packs.

2 5 5 3 2 2 4 3 2 The chargerincludes the power feeding terminals to supply electric power to the assembled battery. The power feeding terminals include at least one pair of terminals, namely, a high-potential terminal and a low-potential terminal. While the assembled batteryis being charged, a potential at the high-potential terminal is higher than a potential at the low-potential terminal. As described above, with the electric toolloaded into the charger, the power feeding terminals of the chargerand the power-receiving terminals of the battery packare mechanically and electrically connected to each other. More specifically, with the electric toolloaded into the charger, the high-potential terminal of the power feeding terminals and the high-potential terminal of the power-receiving terminals are mechanically and electrically connected to each other, and the low-potential terminal of the power feeding terminals and the low-potential terminal of the power-receiving terminals are mechanically and electrically connected to each other.

1 FIG. 2 20 21 22 23 24 25 As shown in, the chargeraccording to this embodiment includes a power supply unit, the charging unit, a battery detection unit, a voltage detection unit, a storage unit, and a control unit.

20 The power supply unitis electrically connected to an external power supply. As used herein, the “external power supply” refers to a grid power supply, a distributed power supply such as a solar battery, and a mobile power supply such as a portable power supply. In this embodiment, the external power supply is supposed to be, for example, a grid power supply.

20 2 21 22 23 24 25 20 2 20 2 2 The power supply unitconverts the electric power supplied from the external power supply into electric power to be supplied to respective components of the charger(namely, the charging unit, the battery detection unit, the voltage detection unit, the storage unit, and the control unit). The power supply unitoutputs the electric power thus converted to the respective components of the charger. More particularly, the power supply unitconverts alternating current power supplied from the grid power supply into direct current power to be supplied to the respective components of the chargerand outputs the direct current power thus converted to the respective components of the charger.

22 21 5 22 3 2 22 2 4 The battery detection unitdetects electrical connection or disconnection between the charging unitand the assembled battery. In other words, the battery detection unitaccording to this embodiment detects that the electric toolis loaded into the charger. The battery detection unitis, for example, a contact sensor provided for the power feeding terminals and detects mechanical connection between the power feeding terminals included in the chargerand the corresponding power-receiving terminals included in the battery pack.

23 5 4 3 2 23 5 23 5 The voltage detection unitdetects a voltage value of the assembled batteryincluded in the battery pack. With the electric toolloaded into the charger, the voltage detection unitaccording to this embodiment detects a voltage value of the assembled battery. The voltage detection unitis, for example, electrically connected to the high-potential terminal and low-potential terminal of the power feeding terminals to detect a voltage value of the assembled batteryby detecting a potential difference between the high-potential terminal and the low-potential terminal.

24 24 25 24 2 The storage unitmay be a semiconductor memory such as a read-only memory (ROM), a random-access memory (RAM), or an electrically erasable programmable read-only memory (EEPROM). Alternatively, the storage unitmay also be a memory of the control unit. Still alternatively, the storage unitmay also be a storage medium such as a memory card to be loaded removably into the charger.

24 5 23 24 251 The storage unitstores a piece of information about the voltage value of the assembled batteryas detected by the voltage detection unit. The storage unitstores a piece of information about a charging condition determined by a condition determiner.

25 25 25 The control unitmay be implemented as, for example, a computer system including one or more processors (microprocessors) and one or more memories. The functions of the control unitare performed by making the one or more processors execute one or more programs stored in the one or more memories. In this embodiment, the program is stored in advance in the memory of the control unit. Alternatively, the program may also be downloaded via a telecommunications line such as the Internet or distributed after having been stored in a non-transitory storage medium such as a memory card.

25 2 25 21 22 23 24 25 251 252 1 FIG. The control unitcontrols the operation of the charger. That is to say, the control unitcontrols the operations of the charging unit, the battery detection unit, the voltage detection unit, and the storage unit. As shown in, the control unitincludes the condition determinerand a charging controller.

251 252 251 252 251 24 The condition determinerdetermines the charging condition for charging control to be performed by the charging controller. Also, the condition determineroutputs a control instruction to the charging controller. In addition, the condition determinerhas the storage unitstore information about the charging condition thus determined. The control instruction is an instruction to start or stop charging. If the control instruction is an instruction to start charging, the control instruction includes a charging condition. The charging condition includes a condition about a current value of the charging current.

251 22 22 3 2 251 5 The condition determinerdetermines, based on the result of detection obtained by the battery detection unit, whether or not charging should be started. When the battery detection unitdetects that the electric toolis loaded into the charger, the condition determinerdetermines that the assembled batterystart to be charged.

251 3 2 3 2 251 5 The condition determinersets a current value of the charging current for the first charging session. As used herein, “the first charging session” refers to the constant current charging session performed for the first time out of constant current charging sessions performed multiple times since the electric toolwas loaded into the chargerand until charging is completed or the electric toolis unloaded from the charger. The current value of the charging current for the first charging session may be a preset value or a current value to be set by the condition determinerbased on a voltage value of the assembled battery, whichever is appropriate. In this embodiment, the current value of the charging current for the first charging session is supposed to be a preset value.

251 23 251 5 251 5 5 251 5 252 5 The condition determinerdetermines, based on the information about the voltage value detected by the voltage detection unit, whether or not charging should be suspended. In other words, the condition determinerdetermines, based on the voltage value of the assembled batteryduring charging, whether or not charging should be suspended. More specifically, the condition determinerdetermines, depending on whether or not the voltage value of the assembled batteryduring charging has reached a predetermined voltage value, whether or not charging should be suspended. When the voltage value of the assembled batteryduring charging is equal to or larger than the predetermined voltage value, the condition determinerdetermines that charging of the assembled batteryshould be suspended and outputs, to the charging controller, an instruction (i.e., a control instruction) to suspend charging of the assembled battery.

5 251 5 3 2 5 251 After the voltage value of the assembled batteryduring charging has reached the predetermined voltage value, the condition determineraccording to this embodiment causes the assembled batteryto be recharged at least once. As used herein, “recharging” refers to a constant current charging session performed, after the electric toolhas been loaded into the charger, on the assembled batteryfor the second time and on. The condition determinersets a current value of the charging current for recharging at a value which is smaller than the current value of the charging current in the previous constant current charging session.

5 21 21 5 5 4 In this case, the voltage value of the assembled batteryincreases from a first voltage value to the predetermined voltage value through the constant current charging session performed by the charging unit. When the constant current charging session by the charging unitis completed, the voltage value of the assembled batteryfalls, due to a voltage drop caused by the charging current and the internal resistance of the assembled battery(or the battery pack), from the predetermined voltage value to a second voltage value. The second voltage value is larger than the first voltage value.

251 251 The condition determinersets a current value of charging current for recharging based on: the difference between the second voltage value when the previous constant current charging session was completed and the first voltage value at the first constant current charging session (i.e., the voltage value when the first constant current charging session was started); and the current value of the charging current for the previous constant current charging session. More specifically, the condition determineraccording to this embodiment sets the current value of the charging current for recharging by the following Equation (1).

th th th 5 In Equation (1), In+1 is a current value of the charging current for recharging (i.e., the (n+1)constant current charging session); In is the current value of the charging current for the previous (i.e., n) constant current charging session; a is a coefficient and is a function that will be a positive constant or a positive value; and ΔVn is the difference between the second voltage value when the previous (i.e., n) constant current charging session was completed and the first voltage value at the first constant current charging session. That is to say, ΔVn indicates how much the voltage has increased, as a result of the n charging sessions, from the initial voltage of the assembled battery. In other words, ΔVn indicates the magnitude of increase in voltage caused by the n charging sessions.

251 23 251 5 251 5 5 251 5 252 5 The condition determinerdetermines, based on the information about the voltage value detected by the voltage detection unit, whether or not recharging should be suspended. In other words, the condition determinerdetermines, based on the voltage value of the assembled batteryduring recharging, whether or not recharging should be suspended. More specifically, the condition determinerdetermines, depending on whether or not a voltage value of the assembled batteryduring recharging has reached a predetermined voltage value, whether or not recharging should be suspended. When the voltage value of the assembled batteryduring recharging is equal to or larger than the predetermined voltage value, the condition determinerdetermines that recharging of the assembled batteryshould be suspended and outputs, to the charging controller, an instruction (i.e., a control instruction) to suspend recharging of the assembled battery. In other words, the instruction to suspend recharging is an instruction to complete charging.

5 251 5 251 5 After the voltage value of the assembled batteryduring charging has reached the predetermined voltage value, the condition determinercauses the assembled batteryto be recharged repeatedly until a predetermined condition is satisfied. As used herein, the “predetermined condition” is that recharging should be completed when the current value of the charging current for the previous charging session changes from a current value larger than the predetermined current value into a current value equal to or smaller than the predetermined current value. That is to say, once recharging is completed, which means that a current value of the charging current during charging is equal to or smaller than the predetermined current value, the condition determinerkeeps the assembled batteryfrom being recharged.

252 21 251 The charging controllercontrols the charging unitin accordance with a control instruction output by the condition determiner.

3 2 21 5 2 4 21 5 4 21 20 5 5 21 252 5 With the electric toolloaded into the charger, the charging unitis electrically connected to the assembled batteryvia, for example, the power feeding terminals included in the chargerand the corresponding power-receiving terminals included in the battery pack. The charging unitis configured to be ready to charge the assembled batteryof the battery packwith electricity. The charging unitconverts direct current power supplied from the power supply unitinto direct current power to be supplied to the assembled battery, and outputs the direct current power thus converted to the assembled battery. The charging unitaccording to this embodiment performs, under the control of the charging controller, the constant current charging session on the assembled battery.

5 21 5 252 252 21 5 5 After the voltage value of the assembled batteryduring charging has reached the predetermined voltage value, the charging unitrecharges the assembled batteryunder the control of the charging controller. Under the control of the charging controller, the charging unitrecharges, at a current value smaller than the current value for the previous constant current charging session, the assembled batteryuntil the voltage value of the assembled batteryduring charging reaches the predetermined voltage value.

2 5 2 5 The chargeraccording to this embodiment allows for reducing, by recharging the assembled batterywith the current value decreased, the magnitude of voltage drop when charging is completed, thus making the voltage value when the charging session is completed closer to a target voltage value (i.e., a voltage value in a fully charged state). That is to say, the chargeraccording to this embodiment allows for controlling charging of the assembled batteryby such a simple control method.

252 21 5 Under the control of the charging controller, the charging unitrecharges the assembled batteryat a current value based on: the difference between the second voltage value when the previous constant current charging session was completed and the first voltage value at the first constant current charging session; and the current value for the previous constant current charging session.

2 5 The chargeraccording to this embodiment allows for recharging the assembled batteryat an appropriate current value because recharging is performed at a current value based on the magnitude of increase in voltage and the current value during the previous charging session.

5 21 252 5 After the voltage value of the assembled batteryduring charging has reached the predetermined voltage value, the charging unitrecharges, under the control of the charging controller, the assembled batteryrepeatedly until a predetermined condition is satisfied.

2 5 2 5 The chargeraccording to this embodiment may bring a voltage value when charging is completed closer to the target voltage value (i.e., a voltage value in a fully charged state) by recharging the assembled batteryrepeatedly with the current value decreased until the predetermined condition is satisfied. That is to say, the chargeraccording to this embodiment allows for controlling charging of the assembled batteryby such a simple control method.

3 FIG. 3 FIG. 3 FIG. 5 3 2 5 1 5 2 5 5 5 5 shows how the voltage value of the assembled batteryand the current value of the charging current change since the electric toolwas loaded into the chargerand until the assembled batteryis fully charged. In, the graph Gis a voltage waveform showing how the voltage value of the assembled batterychanges. The graph Gis a current waveform showing how the current value of the charging current changes. In the example shown in, the initial voltage value of the assembled batteryis Vs, the predetermined voltage value is Vm, the voltage value of the assembled batteryin the fully charged state is V, and the predetermined current value is I.

3 2 0 22 3 2 0 21 1 5 22 5 21 1 2 5 2 5 1 1 1 1 3 FIG. 3 FIG. Suppose that the electric toolis loaded into the chargerat a time t. The battery detection unitdetects that the electric toolis loaded into the chargerat substantially the same timing as the time t. The charging unitstarts, at a time t, charging the assembled batterybased on the result of detection by the battery detection unit. In the example shown in, the initial voltage value of the assembled batteryis Vs. That is to say, the first voltage value for the first charging session is Vs. The charging unitperforms the first constant current charging session during a period between the time tand a time tat which the voltage value of the assembled batteryreaches the predetermined voltage value. When the first constant current charging session is completed, i.e., at a timing immediately after the time t, the voltage value of the assembled batteryfalls from Vm to V. In the example shown in, the current value for the first constant current charging session is I, and the second voltage for the first constant current charging session is V. The value of Vis larger than the value of Vs.

1 5 21 5 21 3 4 5 4 5 2 2 1 2 2 1 1 1 1 2 1 3 FIG. The current value Ifor the first constant current charging session is larger than the predetermined current value I. Thus, the charging unitrecharges the assembled battery. The charging unitperforms the second constant current charging session during a period between a time tand a time tat which the voltage value of the assembled batteryreaches the predetermined voltage value. When the second constant current charging session is completed, i.e., at a timing immediately after the time t, the voltage value of the assembled batteryfalls from Vm to V. In the example shown in, the current value for the second constant current charging session is I, the first voltage is V, and the second voltage is V. Iis a value based on Iand ΔV(i.e., V−Vs) and a value smaller than the value of I. The value of Vis larger than the value of V.

2 5 21 5 21 5 6 5 6 5 3 3 2 3 3 2 2 2 2 3 2 3 FIG. The current value Ifor the second constant current charging session is larger than the predetermined current value I. Thus, the charging unitrecharges the assembled battery. The charging unitperforms the third constant current charging session during a period between a time tand a time tat which the voltage value of the assembled batteryreaches the predetermined voltage value. When the third constant current charging session is completed, i.e., at a timing immediately after the time t, the voltage value of the assembled batteryfalls from Vm to V. In the example shown in, the current value for the third constant current charging session is I, the first voltage is V, and the second voltage is V. Iis a value based on Iand ΔV(i.e., V−Vs) and a value smaller than the value of I. The value of Vis larger than the value of V.

3 5 21 5 21 7 8 5 8 5 4 4 3 4 4 3 3 3 3 4 3 3 FIG. The current value Ifor the third constant current charging session is larger than the predetermined current value I. Thus, the charging unitrecharges the assembled battery. The charging unitperforms the fourth constant current charging session during a period between a time tand a time tat which the voltage value of the assembled batteryreaches the predetermined voltage value. When the fourth constant current charging session is completed, i.e., at a timing immediately after the time t, the voltage value of the assembled batteryfalls from Vm to V. In the example shown in, the current value for the fourth constant current charging session is I, the first voltage is V, and the second voltage is V. Iis a value based on Iand ΔV(i.e., V−Vs) and a value smaller than the value of I. The value of Vis larger than the value of V.

4 5 21 5 21 9 10 5 10 5 5 5 4 5 5 4 4 4 4 5 4 3 FIG. The current value Ifor the fourth constant current charging session is larger than the predetermined current value I. Thus, the charging unitrecharges the assembled battery. The charging unitperforms the fifth constant current charging session during a period between a time tand a time tat which the voltage value of the assembled batteryreaches the predetermined voltage value. When the fifth constant current charging session is completed, i.e., at a timing immediately after the time t, the voltage value of the assembled batteryfalls from Vm to V. In the example shown in, the current value for the fifth constant current charging session is I, the first voltage is V, and the second voltage is V. Iis a value based on Iand ΔV(i.e., V−Vs) and a value smaller than the value of I. The value of Vis larger than the value of V.

5 5 21 5 5 5 5 The current value Ifor the fifth constant current charging session is equal to the predetermined current value I. Thus, the charging unitcompletes the charging session of the assembled battery. Note that Vas the voltage value of assembled batterywhen the fifth charging session is completed is the voltage value of the assembled batteryin a fully charged state.

2 1 2 4 FIG. 4 FIG. Next, an exemplary operation of the chargerincluded in the charging systemwill be described with reference to.is a flowchart showing an exemplary charging method to be performed by the charger.

2 5 2 3 4 2 1 2 3 2 1 2 1 2 3 2 1 2 2 2 3 First, the chargerdetermines whether or not the assembled batteryhas been detected. That is to say, the chargerdetermines whether or not the electric tool(or the battery pack) has been loaded into the charger(in S). If the chargerdetermines that no electric toolhave been loaded into the charger(if the answer is NO in Step S), the chargerrepeats the processing step S. If the chargerdetermines that the electric toolhave been loaded into the charger(if the answer is YES in Step S), the chargersets a current value for the charging current (in S). Then, the chargerstarts a constant current charging session (in S).

2 5 4 2 5 4 2 4 2 5 4 2 5 Next, the chargerdetermines whether or not the voltage value of the assembled batteryhas changed into a voltage value equal to or larger than a predetermined voltage value (in S). If the chargerdetermines that the voltage value of the assembled batterybe smaller than the predetermined voltage value (if the answer is NO in Step S), the chargerrepeats the processing step S. On the other hand, if the chargerdetermines that the voltage value of the assembled batterybe equal to or larger than the predetermined voltage value (if the answer is YES in Step S), the chargerends the constant current charging session (in S).

2 2 6 2 2 6 2 2 6 2 2 6 2 5 Next, the chargerdetermines whether or not the current value set in Step Sis equal to or smaller than the predetermined current value (in S). If the chargerdetermines that the current value set in Step Sbe larger than the predetermined current value (if the answer is NO in Step S), the chargerperforms the series of processing steps S-Sall over again. On the other hand, if the chargerdetermines that the current value set in Step Sbe equal to or smaller than the predetermined current value (if the answer is YES in Step S), the chargerends the charging session of the assembled battery.

4 FIG. 4 FIG. 4 FIG. Note that the flowchart shown inshows only an exemplary procedure and should not be construed as limiting. Optionally, the processing steps shown inmay be performed in a different order from the illustrated one, some of the processing steps shown inmay be omitted as appropriate, and/or an additional processing step may be performed as needed.

Next, variations of the exemplary embodiment will be enumerated one after another.

1 2 5 3 5 5 5 The function of the charging system(or the charger) according to the first embodiment may also be implemented as, for example, a charging method, a (computer) program, or a non-transitory storage medium storing a program thereon. A charging method according to an aspect is performed by one or more processors. The charging method is a method for charging an assembled batteryused in an electric toolwhich includes all-solid-state battery cells. The charging method includes charging the assembled batteryby constant current charging until a voltage value of the assembled batteryduring charging reaches a predetermined voltage value which is larger than a voltage value of the assembled batteryin a fully charged state. A program according to another aspect is designed to cause one or more processors to perform the charging method just described above.

1 2 1 The charging system(or charger) according to the present disclosure or the agent that performs the charging method according to the present disclosure includes a computer system. The computer system includes a processor and a memory as principal hardware components thereof. The computer system performs the functions of the charging systemaccording to the present disclosure or serves as the agent that performs the charging method according to the present disclosure by making the processor execute a program stored in the memory of the computer system. The program may be stored in advance in the memory of the computer system. Alternatively, the program may also be downloaded through a telecommunications line or be distributed after having been recorded in some non-transitory storage medium such as a memory card, an optical disc, or a hard disk drive, any of which is readable for the computer system. The processor of the computer system may be made up of a single or a plurality of electronic circuits including a semiconductor integrated circuit (IC) or a large-scale integrated circuit (LSI). As used herein, the “integrated circuit” such as an IC or an LSI is called by a different name depending on the degree of integration thereof. Examples of the integrated circuits such as an IC or an LSI include integrated circuits called a “system LSI,” a “very-large-scale integrated circuit (VLSI),” and an “ultra-large-scale integrated circuit (ULSI).” Optionally, a field-programmable gate array (FPGA) to be programmed after an LSI has been fabricated or a reconfigurable logic device allowing the connections or circuit sections inside of an LSI to be reconfigured may also be adopted as the processor. Those electronic circuits may be either integrated together on a single chip or distributed on multiple chips, whichever is appropriate. Those multiple chips may be aggregated together in a single device or distributed in multiple devices without limitation. As used herein, the “computer system” includes a microcontroller including one or more processors and one or more memories. Thus, the microcontroller may also be implemented as a single or a plurality of electronic circuits including a semiconductor integrated circuit or a large-scale integrated circuit.

1 1 1 1 2 In the embodiment described above, the plurality of functions of the charging systemare integrated together in a single housing. However, this is not an essential configuration for the charging system. Alternatively, those constituent elements of the charging systemmay be distributed in multiple different housings. Still alternatively, at least some functions of the charging system(e.g., some functions of the charger) may be implemented as a cloud computing system as well.

251 In the embodiment described above, a situation where the condition determinersets a current value of a charging current for a recharging session by Equation (1) has been described as an example. However, this should not be construed as limiting. Alternatively, the current value of the charging current for the recharging session may also be a value that has been set in advance according to the number of times of recharging sessions.

5 3 3 2 If the assembled batteryis built in the electric tool, the electric toolincludes power-receiving terminals which are mechanically and electrically connected to their corresponding power feeding terminals of the charger.

5 5 5 In the embodiment described above, a situation where the assembled batteryincludes a plurality of battery cells has been described as an example. However, this should not be construed as limiting. Alternatively, the assembled batterymay include only one battery cell. That is to say, the assembled batterymay also be configured to include only one all-solid-state battery cell as its battery cell.

In the embodiment described above, a situation where the all-solid-state battery cells are implemented as laminated battery cells (i.e., pouch cells) has been described as an example. However, this should not be construed as limiting. Alternatively, the all-solid-state battery cells may also be implemented as cylindrical battery cells (including button cells) or prismatic cells.

2 3 2 5 2 21 21 5 5 5 As can be seen from the foregoing description of embodiments, a charger () according to a first aspect is used in an electric tool (). The charger () charges an assembled battery (), including an all-solid-state battery, with electricity. The charger () includes a charging unit (). The charging unit () charges the assembled battery () by constant current charging until a voltage value of the assembled battery () during charging reaches a predetermined voltage value which is larger than a voltage value of the assembled battery () in a fully charged state.

5 5 5 This aspect contributes to shortening the charging time of an assembled battery () by charging the assembled battery () by constant current charging until a voltage value during charging reaches a predetermined voltage value which is larger than a voltage value in a fully charged state while the assembled battery (), including an all-solid-state battery which may be charged with a larger current than a lithium-ion battery, is being charged.

2 21 5 5 21 5 5 In a charger () according to a second aspect, which may be implemented in conjunction with the first aspect, the charging unit () recharges the assembled battery () after the voltage value of the assembled battery () during charging has reached the predetermined voltage value. The charging unit () performs a constant current charging session to recharge the assembled battery () at a current value smaller than a current value for a previous constant current charging session until the voltage value of the assembled battery () during charging reaches the predetermined voltage value.

5 This aspect allows for controlling charging of the assembled battery () by a simple control method.

2 5 21 5 21 21 5 In a charger () according to a third aspect, which may be implemented in conjunction with the second aspect, the voltage value of the assembled battery () increases from a first voltage value to the predetermined voltage value through the constant current charging session performed by the charging unit (). The voltage value of the assembled battery () falls from the predetermined voltage value to a second voltage value when the constant current charging session by the charging unit () is completed. The second voltage value is larger than the first voltage value. The charging unit () recharges the assembled battery () at a current value based on: difference between the second voltage value when the previous constant current charging session was completed and the first voltage value at the first constant current charging session; and a current value of the previous constant current charging session.

5 This aspect allows for recharging the assembled battery () at an appropriate current value because recharging is performed at a current value based on the magnitude of increase in voltage and a current value during the previous charging session.

2 21 5 5 In a charger () according to a fourth aspect, which may be implemented in conjunction with the second or third aspect, the charging unit () recharges the assembled battery () repeatedly after the voltage value of the assembled battery () during charging has reached the predetermined voltage value and until a predetermined condition is satisfied. The predetermined condition includes a condition that recharging be completed when a current value for the constant current charging session changes from a current value larger than a predetermined current value into a current value equal to or smaller than the predetermined current value.

5 This aspect allows for controlling charging of the assembled battery () by a simple control method.

2 Note that the constituent elements according to the second to fourth aspects are not essential constituent elements for the charger () but may be omitted as appropriate.

5 3 5 5 5 A charging method according to a fifth aspect is performed by one or more processors. The charging method is a method for charging an assembled battery () used in an electric tool () which includes an all-solid-state battery. The charging method includes charging the assembled battery () by constant current charging until a voltage value of the assembled battery () during charging reaches a predetermined voltage value which is larger than a voltage value of the assembled battery () in a fully charged state.

5 5 5 This aspect contributes to shortening the charging time of an assembled battery () by charging the assembled battery () by constant current charging until a voltage value during charging reaches a predetermined voltage value which is larger than a voltage value in a fully charged state while the assembled battery (), including an all-solid-state battery which may be charged with a larger current than a lithium-ion battery, is being charged.

A program according to a sixth aspect is designed to cause one or more processors to perform the charging method according to the fifth aspect.

5 5 5 This aspect contributes to shortening the charging time of an assembled battery () by charging the assembled battery () by constant current charging until a voltage value during charging reaches a predetermined voltage value which is larger than a voltage value in a fully charged state while the assembled battery (), including an all-solid-state battery which may be charged with a larger current than a lithium-ion battery, is being charged.

2 Charger 21 Charging Unit 3 Electric Tool 5 Assembled Battery